Data validation in Excel is more than just dropdown lists—it’s a powerful safeguard that can prevent costly mistakes before they happen. From blocking duplicates to enforcing formats and date ranges, ...

Most people set up a dropdown list to make spreadsheets smarter with Excel's data validation. However, the Custom option in the Data Validation dialog accepts any formula that returns TRUE or FALSE, ...

I've got an Excel 97 worksheet in which I need to validate some cells. No problem, I'll just use Data->Validate, right? Wrong. The built in validation works well enough as long as the user doesn't ...

Writing code to validate Web-form input can be even more of a chore than implementing form-processing logic. But help is at hand, thanks to the Struts 2 framework. Oleg Mikheev looks under the hood of ...